Digital magnetic wheel logic control network

ABSTRACT

A digital magnetic wheel logic control network for providing selective visual displays wherein the control network has a plurality of inputs, each of which is associated with a particular indicator display. Selective control of any of the inputs will energize one or more of a plurality of control coils of an electromagnetic indicator display cooperatively arranged in relation to a rotary magnet to angularly position the same and thereby provide for a selected indication and including an intermediary network controlled by one of the selective input controls and so arranged in the control network as to dominate the other of the selective input controls so that upon operation of the one input control the rotary magnet is angularly actuated in the electromagnetic indicator display to a position indicative of a failure in a command condition irrespective of any selective control of the other inputs. Further intermediary networks are located between the plurality of inputs and the control coils, each of these other intermediary networks including a plurality of solid-state control elements for selectively controlling energization of different pairs of the control coils to provide selective indications.

United States Patent Cohen [54] DIGITAL MAGNETIC WHEEL LOGIC CONTROL NETWORK [72] Inventor: Richard L. Cohen, Old Bridge, NJ.

[73] Assignee: The Bendix Corporation [22]. Filed: Oct. 19, 1970 [21] Appl. No.: 81,986

[52] US. Cl. ..340/324 R, 340/325, 340/378 R, 340/379 [51] Int. Cl. ..G08b 5/24 [58] Field of Search ..340/324 R, 325, 378 R, 379, 340/334, 166 EL, 343, 344, 336

[56] References Cited UNITED STATES PATENTS 3,218,625 11/1965 Knotowicz ..340/325 X 2,966,616 12/1960 Mash ..340/166 EL X 3,548,403 12/1970 Johnson ..340/324 R 3,560,953 2/1971 Sylvander ..340/324 R X Primary Examiner-David L. Trafton Attorney-Plante, Hartz, Smith & Thompson [451 Oct. 3, 1972 [57] ABSTRACT A digital magnetic wheel logic control network for providing selective visual displays wherein the control network has a plurality of inputs, each of which is associated with a particular indicator display. Selective control of any of the inputs will energize one or more of a plurality of control coils of an electromagnetic indicator display cooperatively arranged in relation to a rotary magnet to angularly position the same and thereby provide for a selected indication and including an intermediary network controlled by one of the selective input controls and so arranged in the control network as to dominate the other of the selective input controls so that upon operation of the one input control the rotary magnet is angularly actuated in the electromagnetic indicator display to a position indicative of a failure in a command condition irrespective of any selective control of the other inputs. Further intermediary networks are located between the plurality of inputs and the control coils, each of these other intermediary networks including a plurality of solid-state control elements for selectively controlling energization of different pairs of the control coils to provide selective indications.

10 Claims, 1 Drawing Figure ,0 mmng U A540 GATE PATENTEDnm e um INVENTOR. R/CHAPD L, COHEN 4 DIGITAL MAGNETIC WHEEL LOGIC CONTROL NETWORK BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a logic control network for providing a plurality of discrete messages by selective energization of control windings of an electromagnetic indicator device.

2. Prior Art The logic control network of the present invention rests in an inventive concept which simplifies the control of the electromagnetic indicator device in requiring far fewer parts than the conventional servoed approach so as to raise the percent of durability and certainty of operation of the electromagnetic indicator device, and effect a condition of greater durability and one which is more sure to produce the desired results in emergency and not only with greater certainty, but with less expense.

Heretofore electromagnetic indicator devices of a type that may be utilized in the digital magnetic wheel logic control network of the present invention have been described and claimed in a US. Pat. No. 3,392,382, granted July 9, 1968 and in a US. Pat. No. 3,465,334, granted Sept. 2, 1969. Both of said patents have been granted to Leonard C. Pursiano and Arnold H. Cohen and assigned to The Bendix Corporation.

Moreover in a US. Pat. No. 3,218,625 granted Nov. 16, l965 to Aloysius E. Knotowicz there is disclosed a plural indication rotatable display system wherein one or more selectively energizable inputs controls the particular indication to be displayed. In FIG. ll of the last mentioned patent, there is shown a solid state control system for an indication system wherein the base inputs of transistors are selectively energized to control the indication to be displayed.

However, the prior art of record does not suggest l) the specific circuitry of the present invention in which an AND gate is so arranged in an intermediary network that upon no message being selected, all inputs to the AND gate will be floating so that the output from the AND gate will saturate a pair of auxiliary control transistors to selectively effect energization of a pair of control coils of a rotary electromagnetic indicator device to position an indicator wheel of the indicator display with a rotary magnet midway between these two control coils.

The prior art of record further fails to suggest a feature (2) of the present invention which resides in another intermediary network controlled by operation of one of the selective input controls and so arranged upon operation of the one selective input control as to render the other of the input controls ineffective to control the electromagnetic indicator while the operation of the one input control effects an angular actuation of the rotary magnet to a position indicating a command condition failure irrespective of any selective operation of the other input controls.

A further novel feature (3) of the present invention, resides in the provision of another intermediary network controlling another pair of transistors so as to selectively effect energization of another pair of said control coils of the electromagnetic indicator device to position the rotary magnet of the indicator wheel to an indicator position midway between the last mentioned other pair of control coils.

Further upon normal operating voltage being supplied to the control network a solenoid is effective to raise an indicator flag or device, while upon a failure in SUMMARY OF THE INVENTION In the simplified arrangement of the present invention, the logic control network includes an AND gate so arranged in an intermediary network that upon no message being selected, all inputs to the AND gate will be floating so that the output from the AND gate will effectively control a pair of auxiliary control transistors so as to selectively effect energization of a pair of control coils of a rotary electromagnetic indicator device to position an indicator wheel of the device with a rotary magnet midway between the pair of energized control coils to provide a no message indication.

Thus an object of the invention is to provide in such a logic control network a simplified arrangement in which an intermediary network is effective to cause energization of a suitable pair of control coils of the electromagnetic indicator device to provide a no message indication, upon the control network being in a no message selected condition.

A further object of the invention is to provide in the logic control network another intermediary network controlling in turn another pair of transistors so as to selectively effect energization of another pair of said control coils of the rotary electromagnetic indicator device to position the rotary magnet of the indicator wheel to a selected indicator position midway between the last mentioned other pair of control coils.

A further object of the invention is to provide another intermediary network between a plurality of the input controls and electromagnetic control coils of the electromagnetic display indicator device and so arranged as to render the input controls ineffective upon operation of another input control to effect actuation of a rotary magnet to an angular position indicative of a command failure condition.

A further object of the invention is to provide a digital magnetic wheel logic control network having a plurality of inputs, each of which is associated with a particular indicator display and including means for selective control of any of the inputs to effectively energize one or more of the control coils of the indicator display or an intermediary network l) for effecting energization of a pair of said control coils and thereby selectively position a rotary magnet of the electromagnetic indicator so as to provide for the selected indication, and including another intermediary network (2) located between the plurality of inputs and the control coils and eflective upon none of the inputs being selectively controlled to effect energization of another pair of the control coils of the indicator device so as to effectively position the rotarymagnet of the device intermediate to the last mentioned other pair of control coils to provide a no message condition indication, and a further overriding intermediary network (3) operable by one of the input controls to render the other input controls ineffective simultaneously with the actuation of the rotary magnet in the electromagnetic indicator to a position indicative of a command failure condition. These and other objects and features of the invention are pointed out in the following description in terms of the embodiment thereof which is shown in the accompanying drawing. It is to be understood however that the drawing is for the purpose of illustration only and is not a definition of the limits of the invention, reference being had to the appended claims for this purpose.

DESCRIPTION OF THE DRAWING The drawing is a schematic wiring diagram of a digital magnetic wheel logic control network embodying the present invention and including a plurality of input controls and intermediary networks for controlling the angular position of a magnetic indicator wheel upon a selected operation of one of said input controls or one of said intermediary networks.

DESCRIPTION OF A PREFERRED EMBODIMENT In the aforenoted U.S. Pat. No. 3,465,334 and No. 3,392,382 there is disclosed an electromagnetic indicator device of a type having a magnetic or permanent magnet rotor angularly positioned by peripheral electromagnets and in the control system of which indicator device there maybe provided a digital magnetic wheel logic control network embodying the present invention.

Referring to the drawing such an electromagnetic indicator device has been designated generally by the numeral l and may include a magnetic rotor 12 selectively angularly positioned by peripheral control electromagnetic windings or coils 14, 16, 18, 20 and 22 respectively.

Each of the control coils or windings 14, 16, 18, 20 and 22 have one endthereof connected by a common conductor 24 through a resistor 26 and a conductor 28 to a switch contact element 30 controlled by a switch arm 32 which is in turn connected through a conductor 34 to a positive terminal of a source of electrical energy or battery 36 having an opposite negative terminal connected through a conductor 38 to ground.

A Zener diode 39 has an anode element connected to ground through a conductor 43 and a cathode element connected to a conductor 41 leading to the input conductor 24. The Zener diode 39 is of a type having a unique reverse current breakdown characteristic which effectsreduction in the back direction upon voltages exceeding a predetermined value being applied to the input conductor 24 so as to maintain the voltage on the input line 24 at a predetermined voltage value.

The voltage maintained on the input conductor 24 at said predetermined valueby the operation of the Zener diode 39 is applied at one end of each of the control windings 14,16, 18, 20 and 22, while opposite other ends of each of the control windings 14, 16, 18, 20 and 22 are connected, respectively, through conductors 44, 46, 48, S0 and 52 to selectively operable means for controlling the energization ,or flow of current through the control windings 14, 16, 18, 20 and 22.

' Thus the conductor 44 leads from the control winding 14 to a collector element 54 of an NPN type transistor 56 and also to a collector element 58 of another NPN type transistor 60. Further the conductor 46 leads from the control winding 16 to a collector element 62 of an NPN type transistor 64, while the condoctor 48 leads from the control winding 18 to a collector element 66 of an NPN type transistor 68 and also to a collector element 70 of another NPN type transistor 72. Moreover the conductor 50 leads from the control winding 20 to a collector element 74 of an NPN type transistor 76 and in addition tov a collector element 78 of another NPN type transistor 80. Furthermore the conductor 52 leads from the control winding 22 to the collector element ,82 of an NPN type transistor 84 and also from the control winding 22 to an anode element 86 of a diode 88 having a cathode element 90 connected by a conductor 92 to a switch contact 94 controlled by switch arm 96 connected by a conductor 98 to ground. Each of the transistors 60, 68, 84 and 76 include emitter. elements 102, 104, 106 and 108, respectively, connected to ground.

Further each of the transistors 68 and 76 have base elements 110 and 112, respectively, connected through resistors 114 and 116 to a conductor 118 leading to a collector element 120 of an NPN type transistor 122. Also connected to the collector element 120 is a resistor 124 leading through a conductor 126 to a positive terminal of a source of electrical energy or battery 128 having a negative terminal connected to ground through a conductor 130. The transistor 122 also has a emitter element 132 connected to ground and a base element 134 connected through a conductor 136 to a collector element 138 of an NPN type transistor 140 having an emitter element 142 connected to a conductor 144 leading to an anode element 146 of a diode 148 having a cathode element 150 connected through a conductor 152 to a switch contact 154 controlled by a switch arm 156 which is in turn connected to ground through the conductor 98.

Each of the transistors 56, 64, 72 and 80, respectively, have emitter elements 160, 162, 164 and 166 connected to anode elements of diodes 170, 172, 174 and 176 respectively. The diodes 170, 172, 174 and 176 have cathode elements connected through, respective, conductors 180, 182, 184 and 186 to switch contacts 190,192, 194 and 196 controlled by, respective, switch arms 200, 202, 204 and 206 connected to ground' through the conductor 98.

Furthermore each of transistors 56, 64, 72, 80 and 140 have base elements 210, 212, 214, 216 and 218, respectively, connected through resistor elements 220, 222, 224, 226 and 228 to a common conductor 230 leading in turn to the conductor 52.

OPERATION OF FIRST INTERMEDIARY NETWORK From the foregoing it will be seen that the transistor 122 and its cooperating circuitry provides a first intermediary network for controlling the operation of the pair of transistors 68 and 76 and in turn effect-upon closure of switch arm 156 energization of the pair of control windings l8 and 20 of the electromagnetic indicator 10 to cause the rotary magnet 12 to be angularly adjusted to a position intermediate the energized control windings 18 and 20 to cause, as shown by the dash lines of the drawing, the electromagnetic indicator device 10 to provide a selected indication, designated as a Wave-Off" indication.

SECOND INTERMEDIARY NETWORK Furthermore an AND gate 250 and its cooperating circuitry provides a second intermediary network for controlling the operation of the pair of transistors 60 and 84 and in turn energization of the pair of control windings 14 and 22, as hereinafter explained.

In controlling the operation of the AND gate 250, there lead from the conductors 44, 46, 48, 50, 136 and 52 controlling energization of the respective windings 14, 16, 18, and 22 of the electromagnetic indicator l0, conductors 264, 266, 268, 270, 272 and 274 which in turn lead to cathode elements 284, 286, 288, 290, 292 and 293, respectively, of control diodes 294, 296, 298, 300, 302 and 303 for the AND gate 250. The, respective control diodes have anode elements connected to a common conductor 304 leading to a base element 306 of an NPN type transistor 308 having a collector element 310 connected by conductor 312 to a positive terminal of a source of electrical energy or battery 314 having a negative terminal connected through a conductor 316 to ground. respective,

A biasing resistor 318 is connected across the base element 306 and collector element 310 of the NPN type transistor 308 so as to apply a positive bias to the base element 306. Further the transistor 308 has an emitter element 320 connected through a resistor 322 to ground and through a conductor 324 and resistors 326 and 328 to the base elements 330 and 332 of the respective NPN type transistors 60 and 84.

OPERATION OF SECOND INTERMEDIARY NETWORK Thus upon the control switch arm 32 being positioned so as to close contact to apply an operating voltage to the input conductor 24 of the control network with the message input selector switches 96, 156, 206, 204, 202 and 200 all being in an open circuit position, as shown by the drawing, or in a no message transmitting condition, a resulting positive bias is applied through'conductors 264, 266, 268, 270, 272 and 274 to the several cathode elements of the control diodes 294, 296, 298, 300, 302 and 303.

In the last mentioned operating condition, the control diodes 294, 296, 298, 300, 302 and 303 are so back biased that the positive bias applied to the base element 306 from the battery 314 through the biasing resistor 318 is effectively maintained to render the NPN type transistor 308 conductive of electrical energy which is in turn applied through the emitter follower resistor 322.

A resultant voltage drop across the emitter follower resistor 322 will in turn apply through the conductor 324 and resistors 326 and 328 a biasing voltage to both the base element 330 and the base element 332 of the transistors 60 and 84 to render these NPN type transistors in turn conductive to effectively energize both of the control windings l4 and 22. This will in turn effect a positioning of the rotary magnet 12 to an angular position intermediate the respective control windings 14 and 22 to cause an indication of a no message transmitting condition of the electromagnetic indicator 10.

However, upon anyone of the selector switch arms 96, 156, 206, 204, 202 or 200 being positioned so as to close the corresponding switch contact controlled thereby, the positive voltage or back bias heretofore applied through the corresponding conductors 264, 266, 268, 270, 272 or 274 will be withdrawn from the cathode element of the corresponding control diode 94, 296, 298, 300, 302 or 303.

The last mentioned action will then in turn divert through such control diode, from which the back bias has been withdrawn, the positive bias heretofore applied to the base element 306 of the transistor 308. The thus effected control diode will then render the transistor 308 nonconductive so as to in turn cause a negative output to be applied through the conductor 324 leading from the AND gate 250 to render both transistors 60 and 84 nonconductive. Thereupon the control windings 14 and 22 will no longer be effectively energized through the transistors 60 and 84 so that the rotor magnet 12 will then be positioned in the electromagnetic indicator device 10 to an angular position dependent upon the energization of the control windings 14, 16, 18, 20 and 22 that has been effected by the selectively closed switch arm 96, 156, 206, 204, 202 or 200, as the case may be.

OPERATION OF THIRD INTERMEDIARY NETWORK Moreover it will be seen that so long as the switch arm 96 remains in an open circuit position, a positive voltage bias will be applied through the common conductor 230 to the base elements of the NPN type transistors 56, 64, 72, and so as to render the same conductive. These transistors 56, 64, 72, 80 and 140 provide in the control network a third intermediary network for conducting electrical energy for energizing the selected control winding or windings of the electromagnetic indicator device 10 upon the closure of the selected switch arm 156, 206, 204, 202 or 200, as the case may be.

However upon the switch arm 96 being selectively operated so as to close the switch contact 94, the positive voltage bias applied through the common conductor 230 of this third intermediary network will be diverted through conductor 52, diode 88 and the closed switch arm 96 leading through conductor 98 to ground. Thereupon the several transistors 56, 64, 72 and 140 of the third intermediary network will be rendered non-conductive and the several switch arms 200, 202, 204, 206 and 156 ineffective for causing selective energization of the control windings 14, 16, 18 and 20 or the selected simultaneous energization of both control windings 18 and 20 upon the switch arm 156 being positioned to close switch contact 154.

Thus, the closure of switch contact 94 by the switch arm 96 will override the selective control that would otherwise be effected by the closure of anyone of the other switch arms 200, 202, 204, 206 and 156. This is a desirable feature of the invention inasmuch as the resultant flow of current through the control winding 22 by the switch arm 96 closing switch contact 94 will effect upon such energization of the control winding 22 an actuation of the rotary magnet 12 to an angular position corresponding to that of the control winding 22 to cause the electromagnetic indicator device 10 to provide a command equipment failure indication, designated as a TILT indication on the drawing by the dash lines.

In this connection, the several message transmitting switch arms 156, 206, 204, 202 and 200 may be automatically operated by suitable means responsive to sensed or command conditions so as to act through the.

control network to cause the angular positioning of the rotary magnet 12 of the electromagnetic indicator device. to provide selected indications of suchsensed or command conditions.

However upon a failure in such automatic operating means, it is essential that energization of the control winding 22 by the closure of switch 96 by operation of other suitable command or failure sensing equipment should dominate the control network so as to cause the rotary magnet 12 to be angularly positioned in the electromagnetic indicator device 10 to a position indicative of a TILT or command equipment failure condition, irrespective of whatever other selected message is being transmitted by the selected closure of one or the other of the aforesaid switch arms 156, 206, 204, 202 and 200.

INPUT VOLTAGE FAILURE INDICATOR Furthermore in order to alert the observer of the indicator 10 to a failure in the operating voltage applied at the input conductor 24, failure in the source of electrical energy 36 or an open circuit condition of the switch arm 32, there is provided a suitable failure indicatormeans operatively connected across the input conductor 24 and ground so as to sense the condition of the operating voltage applied at the input conductor 24.

The last mentioned indicator means may be connected to input conductor 24 by a conductor 342 which leads to one end of a solenoid winding 345 having an opposite end connected through a conductor 347 to ground, The solenoid winding 345 upon effective energization by the input voltage applied across conductor 24 and ground may serve to actuate an armature 349 into the solenoid winding 345 so as to raise an indicator flag 350. The flag 350 is pivotally connected at 352' to the armature 349 and is further pivotally mounted at 354 and biased bya suitable spring 356 so as to drop the flag 350 upon ineffective energization by the input voltage so as to indicate a failure of the operating voltage. Another form of the indicator means may include a suitable shield or indicator element which may be biased by a suitable spring means into a position in front of the indicator wheel 12 upon the control winding 345 of the solenoid operatively connected to the indicator element being effectively deenergized, as upon failure of the source 36 of the operating voltage applied at the input conductor 24 or upon the switcharm 32 being positioned out of contacting relation .with the switch contact 30. The structure and operation of the solenoid 345 and the indicator element or shield positioned thereby maybe similar to that described in the aforenoted US. Pat. No. 3,184,731, granted May 18, 1965 to Milton Brown and assigned to The Bendix Corporation.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangements of the parts, which will not appear obvious to those skilled in the art may be made without departing from the scope of the invention. Reference is, therefore, to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In an electromagnetic indicator of a type for displaying a plurality of discrete indicia in response to electrical energization, said indicator-device being of a type including a magnetic rotor supported for deflection about an axis of rotation thereof to a plurality of discrete angularly spaced positions, a plurality of electromagnetic coils positioned about the axis of rotation of said rotor, and an electrical control network including selectively operable input controls to energize said coils; the improvement comprising in said electrical control network an intermediary control network connected between at least one of the input controls and a plurality of said coils; said intermediary control network including a plurality of control devices, each of said control devices including a control element, and each of said control devices being connected in the intermediary control network in an electrical circuit including means to operate at least a different one of said electromagnetic coils, means to operate the control element of each of said control devices in one selective sense to cause said control devices tobe relatively conductive of electrical energy and in another selective sense to cause said control devices to be relatively non conductive of electrical energy, said control devices being operably connected in the intermediary network to at least one of said input controls was to render the operation of the control elements of each of said plurality of control devices in said one and other selective senses dependent upon a selective operative and inoperative condition of said at least one input control so that a resultant selective energization of said electromagnetic coils may effect actuation of the magnetic rotor of the electromagnetic indicator to predetermined angular positions dependent upon said at least one input control being selectively in said operative and inoperative condition; the plurality of control devices including first and second control devices, and the means to operate the control element of each of said control devices including a main control device having a control element, a source of biasing voltage connected with said main control device in a main control circuit, means operably connecting said main control circuit to the control elements of said first and second devices for controlling the energization of the different electromagnetic coils, and other means operably connecting the control element of the main control device to said at least one input control so that the actuation of the magnetic rotor of the electromagnetic indicator to said predetermined angular positions may be dependent upon said at least one input control being selectively in said operative and inoperative condition; said electrical control network including another between said electromagnetic coils and all of said input controls selectively operable to energize said coils, said other intermediary control network including third and fourth control devices, each of said third and fourth control devices including a control element, each of said third and fourth control devices being connected in said other intermediary control network in a circuit with another different one of said electromagnetic coils, another main control device to operate the control elements of said third and fourth control devices in one selective sense to cause said third and fourth con.- trol devices to be relatively conductive of electrical intermediary control network connected.

energy and in another selective sense to cause said third and fourth control devices to be relatively nonconductive of electrical energy, said other main control device including another control element, a plurality of unidirectional current flow control elements for operably connecting the control element of the other main control device to each of said input controls, said unidirectional current flow control elements being responsive upon at least one of said input controls being in an operative condition to cause the other main control device to operate the control element of each of said third and fourth control devices in said other selective sense so as to effect a simultaneous deenergization of said different electromagnetic coils selectively controlled thereby, and said unidirectional current flow control element being responsive upon all of said input controls being in an inoperative condition to cause the other main control device to operate the control element of each of said third and fourth control devices in said one selective sense.

2. The improvement defined by claim 1 including means operatively connecting said at least'one input control to all of the control elements of said plurality of control devices, and other means operatively connecting each of the control devices in the intermediary control network between other of said input controls and said means to operate at least a different one of said electromagnetic coils so as to render the selective operation of said electromagnetic coils by said other input controls dependent upon a selective operative and inoperative condition to said at least one input control.

3. The improvement defined by claim 1 in which said other operable connecting means includes a plurality of unidirectional current flow control elements for operably connecting the control element of the main control device to each of said input controls, said unidirectional current flow control elements being responsive upon at least one of said input controls being in an operative condition to cause the main control device to operate the control element of each of said first and second control devices in said other selective sense so as to effect a simultaneous deenergization of said different electromagnetic coils selectively controlled thereby, and said unidirectionalcurrent flow control elements being responsive upon all of said input controls being in an inoperative condition to cause the main control device to operate the control element of each of said first and second control devices in said one selective sense so as to effect said simultaneous energization of said different electromagnetic coils selectively controlled thereby.

4. The improvement defined by claim 1 including in said electrical control network another intermediary control network connected between said electromagnetic coils and all of said input controls selectively operable to energize said coils, said other intermediary control network including a plurality of third control devices, each of said third control devices including a control element, the control elements of said third control devices being operable in one sense to cause said third control devices to be relatively conductive of electrical energy and in another selective sense to cause said third control devices to be relatively nonconductive of electrical energy, said plurality of input controls including a main'input control, means operatively connecting said main input control to all of the control elements of said plurality of third control devices, and other means operatively connecting each of the third control devices in the other intermediary control network between other of said input controls and the means to operate at least a different one of said electromagnetic coils so as to render the selective operation of said electromagnetic coils by said other input controls dependent upon a selective operative and inoperative condition of said main input control.

5. The improvement defined by claim 4 including in said electrical network a third intermediary control network connected between said electromagnetic coils and all of said input controls selectively operable to energize said coils, said third intermediary control network including fourth and fifth control devices, each of said fourth and fifth control devices including a control element, each of said fourth and fifth control devices being connected in said third intermediary control network in a circuit with another different one of said electromagnetic coils, a third main control device to operate the control elements of said fourth and fifth control devices in one selective sense to cause said fourth and fifth control devices to be relatively conductive of electrical energy and in another selective sense to cause said fourth and fifth control devices to be relatively non-conductive of electrical energy, said third main control device including another control element, a plurality of unidirectional current flow control elements for operably connecting the control element of the third main control device to each of said input controls, said unidirectional current flow control elements being responsive upon at least one of said input con trols being in an operative condition to cause the third main control device to operative the control element of each of said fourth and fifth control devices in said other selective sense so as to effect a simultaneous deenergization of said different electromagnetic coils selectively controlled thereby, and said unidirectional current flow control elements being responsive upon all of said input controls being in an inoperative condition to cause the third main control device to operate the control element of each of said fourth and fifth control devices in said one selective sense.

6. in a control network for an electromagnetic display of a type including a plurality of control coils, and the control network including a plurality of control inputs for selectively energizing the control coils associated in cooperative relation with an indicator display means, the control network including an intermediary network controlled by one of the selective input controls, and means responsive to selective operation of said one input control in one sense to dominate the other of the selective input controls so as to render the other input controls ineffective to provide a selective energization of the control coils associated therewith so long as said one input control remains in said operative condition of said one sense and effective to provide selective energization of another of said control coils to cause said display means associated therewith to provide an indication of the operative condition of said one input control in said one sense, and other means responsive to selective operation of said one input control in another sense to effectively deenergize saidother of said control coils and render the other of said input controls effective to provide selective energization of the control coils associated therewith so long as said other of said input controls remains in said operative condition to said other sense. 7. In a control network for an electromagnetic display of a type including a plurality of control coils, and the control network including a plurality of control inputs for selectively energizing the control coils associated in cooperative relation with an indicator dis-- play means, the control network including an intermediary network including means operative upon all of said input controls being in an inoperative condition to cause selective energization of said control coils in one sense to thereby cause said display means associated therewith to provide an indication of said inoperative condition of said input controls, and other means responsive upon anyone of said input controls being in an operative condition to present said operative means from causing the selective energization of said control coils in said one sense, whereupon the said control coils may be selectively energized in another sense dependent upon the one input control being in said operative condition; the control network including another intermediary network controlled by one of the selective input controls, and means responsive to selective operation of said one input control in one sense to dominate the other of the selective input controls so as to render the other input controls ineffective to provide a selective energization of the control coils associated therewith so long as said one input control remains in said operative condition of said one sense and effective to provide selective energization of another of said control coils to cause said display means associate therewith to provide an indication of the operative condition of said one input control in said ohe sense, and other means responsive to selective operation of said one input control in another sense to effectively deenergize said other of said control coils and render the other of said input controls effective to provide selective energization of the control coils associated therewith so long as said other of said input controls remains in said operative condition of said other sense.

8. In a control network for an electromagnetic display of a type including a plurality of control coils, and the control network including a plurality of control inputs for selectively energizing the control coils associated in cooperative relation with an indicator display means, the control network including an intermediary network controlled by said input controls, the intermediary network including means responsive to operation of a first of said input controls operative to effect simultaneous energization of a pair of said control coils, a second of said input controls operative to effect selective energization of one of said control coils of said pair of control coils, and a third of said input controls operative to effect selective energization of the other of said control coils of said pair of control coils, and means responsive to operation of one of said aforementioned input controls for rendering the other of said input controls ineffective to provide the foregoing selective energization of said control coils so long as said one input control remains in an operative condi- 5 .111 a control network of a type defined by claim 8 in which the control network includes another intermediary network including means operative upon all of said input controls being in an inoperative condition to cause selective energization of said control coils in one sense to thereby cause said display means associated therewith to provide an indication of said inoperative condition of said input controls, and other means responsive upon anyone of said input controls being in an operative condition to prevent said operative means from causing the selective energization of said control coils in said one sense, whereupon the said control coils may be selectively energized in another sense dependent upon the one input control being in said operative condition 10. In a control network of a type defined by claim 9 in which the operation of said one input control effects a selective energization of said control coils to cause said display means associated therewith to provide an indication of the operative condition of said one input control. 

1. In an electromagnetic indicator of a type for displaying a plurality of discrete indicia in response to electrical energization, said indicator device being of a type including a magnetic rotor supported for deflection about an axis of rotation thereof to a plurality of discrete angularly spaced positions, a plurality of electromagnetic coils positioned about the axis of rotation of said rotor, and an electrical control network including selectively operable input controls to energize said coils; the improvement comprising in said electrical control network an intermediary control network connected between at least one of the input controls and a plurality of said coils; said intermediary control network including a plurality of control devices, each of said control devices including a control element, and each of said control devices being connected in the intermediary control network in an electrical circuit including means to operate at least a different one of said electromagnetic coils, means to operate the control element of each of said control devices in one selective sense to cause said control devices to be relatively conductive of electrical energy and in another selective sense to cause said control devices to be relatively non-conductive of electrical energy, said control devices being operably connected in the intermediary network to at least one of said input controls so as to render the operation of the control elements of each of said plurality of control devices in said one and other selective senses dependent upon a selective operative and inoperative condition of said at least one input control so that a resultant selective energization of said electromagnetic coils may effect actuation of the magnetic rotor of the electromagnetic indicator to predetermined angular positions dependent upon said at least one input control being selectively in said operative and inoperative condition; the plurality of control devices including first and second control devices, and the means to operate the control element of each of said control devices including a main control device having a control element, a source of biasing voltage connected with said main control device in a main control circuit, means operably connecting said main control circuit to the control elements of said first and second devices for controlling the energization of the different electromagnetic coils, and other means operably connecting the control element of the main control device to said at least one input control so that the actuation of the magnetic rotor of the electromagnetic indicator to said predetermined angular positions may be dependent upon said at least one input control being selectively in said operative and inoperative condition; said electrical control network including another intermediary control network connected between said electromagnetic coils and all of said input controls selectively operable to energize said coils, said other intermediary control network including third and fourth control devices, each of said third and fourth control devices including a control element, each of said third and fourth control devices being connected in said other intermediary control Network in a circuit with another different one of said electromagnetic coils, another main control device to operate the control elements of said third and fourth control devices in one selective sense to cause said third and fourth control devices to be relatively conductive of electrical energy and in another selective sense to cause said third and fourth control devices to be relatively non-conductive of electrical energy, said other main control device including another control element, a plurality of unidirectional current flow control elements for operably connecting the control element of the other main control device to each of said input controls, said unidirectional current flow control elements being responsive upon at least one of said input controls being in an operative condition to cause the other main control device to operate the control element of each of said third and fourth control devices in said other selective sense so as to effect a simultaneous deenergization of said different electromagnetic coils selectively controlled thereby, and said unidirectional current flow control element being responsive upon all of said input controls being in an inoperative condition to cause the other main control device to operate the control element of each of said third and fourth control devices in said one selective sense.
 2. The improvement defined by claim 1 including means operatively connecting said at least one input control to all of the control elements of said plurality of control devices, and other means operatively connecting each of the control devices in the intermediary control network between other of said input controls and said means to operate at least a different one of said electromagnetic coils so as to render the selective operation of said electromagnetic coils by said other input controls dependent upon a selective operative and inoperative condition to said at least one input control.
 3. The improvement defined by claim 1 in which said other operable connecting means includes a plurality of unidirectional current flow control elements for operably connecting the control element of the main control device to each of said input controls, said unidirectional current flow control elements being responsive upon at least one of said input controls being in an operative condition to cause the main control device to operate the control element of each of said first and second control devices in said other selective sense so as to effect a simultaneous deenergization of said different electromagnetic coils selectively controlled thereby, and said unidirectional current flow control elements being responsive upon all of said input controls being in an inoperative condition to cause the main control device to operate the control element of each of said first and second control devices in said one selective sense so as to effect said simultaneous energization of said different electromagnetic coils selectively controlled thereby.
 4. The improvement defined by claim 1 including in said electrical control network another intermediary control network connected between said electromagnetic coils and all of said input controls selectively operable to energize said coils, said other intermediary control network including a plurality of third control devices, each of said third control devices including a control element, the control elements of said third control devices being operable in one sense to cause said third control devices to be relatively conductive of electrical energy and in another selective sense to cause said third control devices to be relatively non-conductive of electrical energy, said plurality of input controls including a main input control, means operatively connecting said main input control to all of the control elements of said plurality of third control devices, and other means operatively connecting each of the third control devices in the other intermediary control network between other of said input controls and the mEans to operate at least a different one of said electromagnetic coils so as to render the selective operation of said electromagnetic coils by said other input controls dependent upon a selective operative and inoperative condition of said main input control.
 5. The improvement defined by claim 4 including in said electrical network a third intermediary control network connected between said electromagnetic coils and all of said input controls selectively operable to energize said coils, said third intermediary control network including fourth and fifth control devices, each of said fourth and fifth control devices including a control element, each of said fourth and fifth control devices being connected in said third intermediary control network in a circuit with another different one of said electromagnetic coils, a third main control device to operate the control elements of said fourth and fifth control devices in one selective sense to cause said fourth and fifth control devices to be relatively conductive of electrical energy and in another selective sense to cause said fourth and fifth control devices to be relatively non-conductive of electrical energy, said third main control device including another control element, a plurality of unidirectional current flow control elements for operably connecting the control element of the third main control device to each of said input controls, said unidirectional current flow control elements being responsive upon at least one of said input controls being in an operative condition to cause the third main control device to operative the control element of each of said fourth and fifth control devices in said other selective sense so as to effect a simultaneous deenergization of said different electromagnetic coils selectively controlled thereby, and said unidirectional current flow control elements being responsive upon all of said input controls being in an inoperative condition to cause the third main control device to operate the control element of each of said fourth and fifth control devices in said one selective sense.
 6. In a control network for an electromagnetic display of a type including a plurality of control coils, and the control network including a plurality of control inputs for selectively energizing the control coils associated in cooperative relation with an indicator display means, the control network including an intermediary network controlled by one of the selective input controls, and means responsive to selective operation of said one input control in one sense to dominate the other of the selective input controls so as to render the other input controls ineffective to provide a selective energization of the control coils associated therewith so long as said one input control remains in said operative condition of said one sense and effective to provide selective energization of another of said control coils to cause said display means associated therewith to provide an indication of the operative condition of said one input control in said one sense, and other means responsive to selective operation of said one input control in another sense to effectively deenergize said other of said control coils and render the other of said input controls effective to provide selective energization of the control coils associated therewith so long as said other of said input controls remains in said operative condition to said other sense.
 7. In a control network for an electromagnetic display of a type including a plurality of control coils, and the control network including a plurality of control inputs for selectively energizing the control coils associated in cooperative relation with an indicator display means, the control network including an intermediary network including means operative upon all of said input controls being in an inoperative condition to cause selective energization of said control coils in one sense to thereby cause said display means associated therewith to provide an indIcation of said inoperative condition of said input controls, and other means responsive upon anyone of said input controls being in an operative condition to present said operative means from causing the selective energization of said control coils in said one sense, whereupon the said control coils may be selectively energized in another sense dependent upon the one input control being in said operative condition; the control network including another intermediary network controlled by one of the selective input controls, and means responsive to selective operation of said one input control in one sense to dominate the other of the selective input controls so as to render the other input controls ineffective to provide a selective energization of the control coils associated therewith so long as said one input control remains in said operative condition of said one sense and effective to provide selective energization of another of said control coils to cause said display means associate therewith to provide an indication of the operative condition of said one input control in said one sense, and other means responsive to selective operation of said one input control in another sense to effectively deenergize said other of said control coils and render the other of said input controls effective to provide selective energization of the control coils associated therewith so long as said other of said input controls remains in said operative condition of said other sense.
 8. In a control network for an electromagnetic display of a type including a plurality of control coils, and the control network including a plurality of control inputs for selectively energizing the control coils associated in cooperative relation with an indicator display means, the control network including an intermediary network controlled by said input controls, the intermediary network including means responsive to operation of a first of said input controls operative to effect simultaneous energization of a pair of said control coils, a second of said input controls operative to effect selective energization of one of said control coils of said pair of control coils, and a third of said input controls operative to effect selective energization of the other of said control coils of said pair of control coils, and means responsive to operation of one of said aforementioned input controls for rendering the other of said input controls ineffective to provide the foregoing selective energization of said control coils so long as said one input control remains in an operative condition.
 9. In a control network of a type defined by claim 8 in which the control network includes another intermediary network including means operative upon all of said input controls being in an inoperative condition to cause selective energization of said control coils in one sense to thereby cause said display means associated therewith to provide an indication of said inoperative condition of said input controls, and other means responsive upon anyone of said input controls being in an operative condition to prevent said operative means from causing the selective energization of said control coils in said one sense, whereupon the said control coils may be selectively energized in another sense dependent upon the one input control being in said operative condition.
 10. In a control network of a type defined by claim 9 in which the operation of said one input control effects a selective energization of said control coils to cause said display means associated therewith to provide an indication of the operative condition of said one input control. 